The present invention is related to terahertz frequency spectrometers and, more particularly, to an advanced apparatus, system and methods for reducing or eliminating photo-mixing interference patterns from detector photoconductive switch detector signals.
Terahertz frequency spectrometers can utilize photoconductive switches and light sources to generate signals in frequencies ranging from tens of MHz to tens of THz. The light sources can be frequency tunable lasers such as Distributed Feedback Lasers (DFB) which have a light output frequency that can be controlled using temperature. The terahertz frequency can be created by generating two lights at frequencies that are different from one another and applying the two lights to a source photoconductive switch. The same two lights can be applied to a detector photoconductive switch to homodyne detect the high frequency created by the source photoconductor.
Terahertz frequency electromagnetic radiation in the sub-millimeter and terahertz (THz) frequency ranges has been employed for characterizing molecular gases, including materials of atmospheric importance. Recently, terahertz radiation has been utilized for the characterization and/or detection of solids as well as gases. Many different materials have distinct and measurable information signatures in the terahertz frequency range. For example, these materials can absorb electromagnetic radiation at certain terahertz frequencies that are unique for a given material or materials and which can be used to identify the given material. Materials that exhibit these information signatures include: illicit drugs, biologically important compounds such as sugars and hormones, and explosives. Terahertz radiation can also be used in the field of art conservation, for example, to determine the proper materials for restoring paintings.
Many dielectric, nonmetallic materials are transparent at terahertz frequencies which makes it is possible to measure or detect other materials that are hidden behind such terahertz transparent materials. Some examples of terahertz transparent materials include: fabrics, packaging materials, and paper. Also, in the case of art characterization, layers of paint are also transparent to terahertz frequency radiation. Nonpolar liquids are also transparent to terahertz radiation.
In addition, terahertz radiation is non-ionizing and is completely eye safe. Because of this, terahertz radiation can be used in public areas without the risk of harm to humans, flora, or fauna. This can be especially beneficial because people using the terahertz frequency radiation are not encumbered by unwieldy radiation protection such as is common, for example, when using x-rays.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon reading of the specification and a study of the drawings.